Two-module-read, read-after-write, bi-directional tape drive

ABSTRACT

A digital tape drive wherein tape is written, and a read-after-write operation is immediately performed to check the integrity of the write operation, for either direction of tape movement. The tape contains a plurality of parallel data tracks. Two read/write head modules span the entire tape. The read and write gaps of each module are alternately spaced across the width of the tape, such that the write gaps of one module are aligned with the read gaps of the other module. When one module is selected for writing, as a function of the direction of tape movement, the other module is selected to read-after-write check the first module&#39;s written data. One module writes odd-track data during one direction of tape movement, and reads even-track data during the opposite direction of tape movement; as the other module writes even-track data during said opposite movement direction, and reads odd-track data during said one movement direction. Common read and write eletronic circuits are switched between the two modules, since each module is using only one of its read and write gap multiples at any given time.

TECHNICAL FIELD

This invention relates to the field of magnetic recording, and morespecifically to the field of multiple channel recording wherein magneticmedia carries multiple, parallel data channels, certain (odd) tracks ofwhich are operable during one direction of media movement and other(even) tracks of which are operable during the opposite direction ofmedia movement.

BACKGROUND OF THE INVENTION

Bi-directional tape drives, both digital and analog, are well known. Thestate-of-the-art in digital recording is that digital data should beread immediately after being written, in order to insure that the datahas been written correctly. For example, a write-head-module is placedin front of a read-head-module, in the direction of tape movement. Thesetwo head modules are preferably formed as a single physical unit; thus,the read and write gaps are closely spaced. This arrangement, however,requires two write modules and two read modules for a bi-directionaltape drive. One pair of head modules operate on the tape's odd-numbertracks, and the other head module pair operate on the even-number tracksduring the opposite direction of tape movement.

While a number of prior art arrangements of this type exist, U.S. Pat.No. 3,942,190 is cited as exemplary. In this device, one group of headsis operable during one direction of tape movement, and another group ofheads operates during the opposite direction of tape movement. Sinceonly one group of heads operates at a time, a head switching circuitallows a common amplifier to be used by the operative group of heads.

U.S. Pat. No. 3,813,690 provides a somewhat similar teaching.

SUMMARY OF THE INVENTION

The present invention provides a bi-directional media drive which doesnot require the complexity of head construction provided by the priorart, and yet, none of the function is eliminated.

More specifically, the present invention provides accessing ofodd-number tracks during one direction of tape movement, andeven-numbered tracks during the opposite direction of tape movement,while accomplishing read-after-write checking, but with a simplifiedhead construction and arrangement.

This head construction and arrangement provides two head modules, eachhaving one gap line which traverses all data tracks, both odd and even.Each module's gap line contains alternating write and read gaps,occupying a common line which extends transverse (i.e., perpendicularto) the direction of tape movement. The construction of the headpreferably provides write-wide and read-narrow operation.

These two head modules are closely spaced, in the direction of tapemovement, and in fact they are preferably formed as a single physicalunit. The write gaps of one module are aligned, in the direction of tapemovement, with the read gaps of the other module. Thus, one module isthe write-module for say the even tracks, as the other module is theread-after-write module for the even tracks, and vice versa.

One set of write electronic circuits, and one set of read electroniccircuits, are shared by the two modules, as a function of the directionof tape movement.

The foregoing and other features and advantages of the invention will beapparent from the following more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a top view of a length of magnetic tape, and its relationshipto the head of the present invention;

FIG. 2 shows a portion of the head of FIG. 1, as it would look when madeusing thin film techniques to manufacture the head; and

FIG. 3 shows an arrangement for switching the read/write electronicnetwork as a function of the direction of tape movement.

THE INVENTION

The tape drive per se to be used in practicing the present invention canbe of any well known configuration. Reel-to-reel and buffered tapedrives are two well known drives, either of which is suitable.

The head to be used in the practice of the present invention can alsotake the form of any of a number of well known construction andarrangements. However, thin film construction is preferred. By the useof photolithographic, printed circuit techniques, it is possible tomaximize use of the media's surface, since narrow, closely spaced,tracks can be written. Whatever type head is used in the practice of thepresent invention, the present invention provides the advantage thattransversely adjacent head elements (i.e., head elements spaced in adirection normal to the direction of media movement) are not operativeat the same time, thus minimizing the possibility of cross talk and thelike.

In the preferred embodiment of a thin film head, the write element andthe read element can both be inductive elements; however, it ispreferred that the read element be a magnetoresistive (MR) element. Itis also preferred that such MR read gaps be of the shunt biased type,well known to those of skill in the art.

Whatever the head construction chosen by those skilled in the art, it ispreferred that the head construction implement the well known write-wideread-narrow format.

While the present invention is described in an environment where theread and write gaps are used in immediately alternating, odd/evenfashion, the term alternating is intended to include other formats. Forexample, it is within the present invention to provide a format of 20tracks across the width of the media, hereinafter called tape. Oneformat, within the present invention, provides that tracks 1, 3, 5, 7,9, 11, 13, 15, 17 and 19 are operative during forward tape movement,while tracks 2, 4, 6, 8, 10, 12, 14, 16 18 and 20 are operative duringthe opposite direction of tape movement. Another format, also within thepresent invention, provides for tracks 1, 5, 9, 13 and 17 to beoperative during a first forward pass of the tape, with tracks 3, 7, 11,15 and 19 being operative during a second forward pass. Of course,during the reverse pass, which separates the first and second forwardpasses, tracks 2, 6, 10, 14 and 18 are operative, and tracks 4, 8, 12,16 and 20 are operative during the next reverse pass of the tape.

Other formats usable in the practice of the present invention will ofcourse be evident to those of skill in the art, and are considered to bewithin the teaching of the present invention.

Reference numeral 10 designates a length of flexible magnetic recordingtape of, for example 1/2 inch width, and of conventional chemicalformulation. Arrow 11 designates the tape's forward movement direction,and arrow 12 designates the reverse direction. Magnetic read/writetransducer or head 13 is made up of two modules 14 and 15 of generallyidentical construction. These two modules are mounted together to form asingle physical unit. In this way, the transducing gaps of one moduleare not only closely spaced to the gaps of the other unit, but also, themodule gaps are accurately aligned in the direction of tape movement.

In the exemplary head of FIG. 1, each module includes one gap line, 20and 21, along which the individual gaps of each module are accuratelylocated. As those skilled in the art will appreciate, it is essentialthat gap lines 20 and 21 be parallel, and that the head be mounted tothe tape drive (not shown) in an accurate manner, such that gap lines 20and 21 are perpendicular to the direction of tape movement 12, 13.

In order to simplify the showing of the present invention, only the tapedrive's head is shown. It is contemplated, and it is a part of thisdisclosure, that head 13 forms a part of, and is mounted to, a tapedrive of whatever form is chosen by those desiring to use the presentinvention.

Within the teachings of the present invention, head 13 includesalternating read/write gaps along the length of each of the gap lines20, 21 which extend transverse to the direction of tape movement 11, 12.

In this exemplary embodiment, tape 11 is shown as having 18 tracksacross its 1/2 inch width. As shown in FIG. 1, track "1" is at the leftedge of the tape, and track "18" is at the right edge of the track.These tracks are for example 0.020 inch wide, as determined by the widthof the head's write gaps. The tracks are written about 15% wider thanthe read gaps are able to read; i.e., the head's write track widths are15% wider than are its read track widths. FIG. 1 shows the gapsidentified as "1" through "18", as these gaps individually cooperatewith an identically numbered tape track. FIG. 1 also identifies theeighteen individual read gaps as "R" and the eighteen write gaps as "W".Within the teachings of the present invention, the read gaps of onemodule are aligned, in the direction of tape movement, with the writegaps of the other module. Thus, as seen in FIG. 1, module 14's track-1write gap 30 is aligned with module 15's track-1 read gap 31. Write gap30 writes a 15% wider track-1, on tape 10, than is read by gap 31.

As stated, the construction and arrangement of head 13 is not criticalto the present invention. However, a thin film head is preferred. FIG. 2shows a portion of such a thin film head. In this figure, two writecoils 40 and 41 are shown deposited on ferrite substrate 42, with ashunt-biased magnetoresistive read element 43 deposited therebetween. Ahead in accordance with the present invention, and in accordance withthe embodiment of FIG. 1, would have two modules, each module havingnine such read elements, and nine such write elements.

FIG. 3 shows a reel-to-reel tape drive using the above-describedconstructions and arrangements. Since the details of many reel-to-reeltape drives are known, FIG. 3 is a simplified showing.

A pair of tape reels 100 and 101 store a length of tape 10. Each reel iscapable of bi-directional rotation, as is controlled by motors 102 and103. These motors are controlled by a reel servo network 104, by way ofconductors 105 and 106, all under the command of input conductor 107.

The two aforesaid head modules 14, 15 have their read and write gapelements connected to read and write electronic network 108, by way ofmulticonductor buses 109 and 110. Network 108 accepts digital data to bewritten onto tape, by way of multiconductor bus 111; and digital dataread from tape is supplied to a using system by way of multiconductorbus 112.

Buses 111 and 112, as well as the write portions and the read portionsof network 108, are switched between the write and read gaps of headmodules 14 and 15, in accordance with the direction of tape movement, asthis direction is indicated to network 108 by the signal on conductor120.

The details of FIG. 3 are not to be taken as a limitation on the presentinvention. Countless other tape drive configurations will be apparent tothose skilled in the art for use with the present invention.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

I claim as my invention:
 1. In a bi-directional media drive wherein datais written on certain odd-numbered tracks during one direction of mediamovement, and is written on certain even-numbered tracks during theopposite direction of media movement, and in which a read-after-writecheck is immediately performed on written data, the improvementcomprising:two data-transducing head modules, each of which includes onetransducing gap line extending normal to the direction of mediamovement, said modules being non-movable relative each other; and eachgap line including alternating write and read gaps, the write gaps ofone module being aligned in the direction of media movement with theread gaps of the other module.
 2. The drive of claim 1 including means,responsive to the direction of media movement and to a write state ofsaid media drive, for enabling certain write gaps of one module and thealigned read gaps of the other module during one direction of mediamovement, and for enabling other aligned write and read gaps during theother direction of media movement.
 3. The drive of claim 2 wherein thedrive is a magnetic tape drive, said media is magnetic tape, and saidheads are magnetic heads.
 4. The drive of claim 3 wherein said writegaps are wider than are said read gaps, said width parameter beingmeasured generally normal to the direction of tape movement.
 5. Thedrive of claim 2 including read electronic circuits and write electroniccircuits, and switching means, controlled as a function of mediamovement, to connect said read and write circuits only to the read andwrite gaps which are operative for that direction of media movement. 6.The drive of claim 1 wherein said heads are thin film heads.
 7. Thedrive of claim 6 wherein the read gap of said thin film heads aremagnetoresistive.
 8. The drive of claim 2 wherein said heads are thinfilm heads.
 9. The drive of claim 8 wherein the read gap of said thinfilm heads are magnetoresistive.
 10. The drive of claim 1 wherein allwrite gaps of one module are operative with all read gaps of the othermodule during on direction of tape movement.
 11. The drive of claim 2wherein all write gaps of one module are operative with all read gaps ofthe other module during one direction of tape movement.
 12. The drive ofclaim 11 wherein said heads are thin film heads.
 13. The drive of claim12 wherein the read gap of said thin film heads are magnetoresistive,and wherein said heads provide wide-write, narrow-read.